Is it “safe” to cache IServiceProvider for an app's lifetime?

Question

I\'m using ASP.NET Core, and its builtin DI container. I\'m using a third-party library (NLog) which I can\'t change.

My Foo class has a dependency (by

Answer 1

You don't want to inject your IoC container anywhere. That's a bad practice that allows for sloppy coding, and makes unit testing harder, amongst many other reasons.

Instead introduce a factory that can be injected and create a context on demand:

public interface IDbContextFactory
{
    TContext Create();
}

public class DbContextFactory : IDbContextFactory
    where TContext : DbContext
{
    private readonly Func _contextCreator;

    public DbContextFactory(Func contextCreator)
    {
        _contextCreator = contextCreator;
    }

    public TContext Create()
    {
        return _contextCreator();
    }
}

Now if you inject this into your Foo:

public class Foo 
{
    private readonly IDbContextFactory _contextFactory;
    public Foo(IDbContextFactory contextFactory)
    { 
        _contextFactory = contextFactory;
    }

    public void bar() {
    {
        using (var context = _contextFactory.Create())
        {
            // use your freshly instantiated context
        }
    }
}

Any decent dependency injection framework can resolve the Func parameter of the DbContextFactory, and pass a func there that creates an instance per request.